Shelving by subject or by author: choose once

Home libraries are almost always arranged by a blend: a bit of subject, a bit of size, a bit of wherever there was room. The blend works as long as you remember why. Once you forget, nothing can be found.

By subject

The natural choice when you read to learn: law, history, poetry, theology. You find things by thinking of the topic, and neighbouring books talk to each other.

Its weakness is that a book often belongs to two subjects. Pick the one you'll use most and leave the other to the record.

By author

It suits a literature collection better, where you look for a name more than a subject. Alphabetical order asks for no decisions, which is a virtue.

For Arabic names, decide in advance whether to file by family name, given name or the name the author is known by (Ibn Taymiyya under I or T), and keep to it.

What the record settles

Shelving and cataloguing are two separate jobs. The shelf follows one rule; the record carries every classification at once: subject, author, language, reading status. You can search in any direction without moving a single volume.